1. Field of the Invention
The present invention relates to an integrated circuit device with a built-in monolithic temperature sensor.
2. Description of the Related Art
Recently, there are growing needs for monitoring the operation temperature of an integrated circuit device for the purpose of preventing thermal breakdown of devices in the integrated circuit device and stabilizing the operation of a device whose characteristic has a temperature dependence.
In this respect, Japanese Patent Laid-Open Publication No. H1-302849, for example, discloses a technique of protecting an LSI (Large Scale Integrated circuit-) in a semiconductor integrated circuit device from thermal breakdown by a temperature rise by providing a temperature sensor on the same substrate as that of the LSI, deciding that the LSI is abnormally overheated when the temperature detected by the temperature sensor exceeds a predetermined value and then shutting down the LSI. Japanese Patent Laid-Open Publication No. H9-229778, for example, proposes the technique of using a parasitic pn junction diode as such a temperature sensor.
The technique that uses a parasitic pn diode as a temperature sensor has a problem such that as the temperature coefficient of the parasitic pn junction diode is as low as 0.2 (%/K), a sufficient SNR (Signal-to-Noise Ratio) cannot be acquired.
Japanese Patent Laid-Open Publication No. 2003-344181, for example, discloses a technique of measuring the temperature by providing two frequency-dividing circuits in each of which a resistance having a positive temperature coefficient and a resistance having a negative temperature coefficient are connected in series. In the art disclosed in Japanese Patent Laid-Open Publication No. 2003-344181, the diffusion resistance of a P-type diffusion layer is used as the resistance whose electric resistivity has a positive temperature coefficient, and a polysilicon layer is used as the resistance whose electric resistivity has a negative temperature coefficient.
However, the electric resistivitys of the diffusion resistance and polysilicon used in Japanese Patent Laid-Open Publication No. 2003-344181 have considerably small temperature coefficients. Even when those resistances are connected in series, the temperature cannot be measured with sufficiently high precision.
The present inventors have developed a technique of forming an vanadium oxide film as a resistance having an electric resistivity whose temperature coefficient has a large absolute value, and has disclosed it in Japanese Patent Laid-Open Publication No. H11-330051.
The prior art technique suffers the following problems. When a temperature sensor is formed in a semiconductor integrated circuit device using a special material, such as vanadium oxide, which is not used in the normal semiconductor process, the special material contaminates the semiconductor integrated circuit device, which may adversely affect the operation of the other portion of the semiconductor integrated circuit device than the temperature sensor. The special material is also likely to contaminate the manufacture equipment for the semiconductor integrated circuit device so that other semiconductor integrated circuit devices manufactured by that equipment are also contaminated.